G20峰会期间杭州地区空气质量特征及气象条件分析

利用空气质量和气象要素的监测资料与再分析资料,分析了2016年G20峰会期间(2016年8月10日—9月20日)杭州及周边地区空气质量演变及区域特征,探讨了气象条件对G20峰会期间杭州空气质量的影响.结果表明:G20峰会管控期间,由于机动车排放大幅度降低,杭州NO_2浓度较管控前有所下降,对比周边城市降幅居于首位;而由于不利气象条件的影响,PM_(2.5)、PM_(10)、SO_2、CO和O_3浓度比管控前有不同程度的增长,但增幅相比周边城市较小,说明管控措施对杭州空气质量有一定的改善效果.9月7日管控措施结束后污染反弹现象明显.气象条件对杭州的空气质量有重要影响:在管控前,杭州晴热高温天气有利于O3的生成,偏东风相对洁净,污染传输较少;在管控期,杭州虽受到静稳天气和外来污染传输的影响,但得益于减排应急管控措施的有效实施,NO_2浓度下降幅度最大,其他污染物的增幅也较周边城市偏小;在管控后,气象条件不利于污染物的垂直扩散,受静稳天气和污染源恢复常态的影响,PM_(2.5)、PM_(10)、NO_2、SO_2和CO出现了整个研究时段的最大值,而台风"莫兰蒂"使得杭州PM_(2.5)、PM_(10)和O_3浓度出现了整个研究时段的最低值.

Analysis on air quality characteristics and meteorological conditions in Hangzhou during the G20 summit

Based on the observation data of air quality and meteorological elements and reanalysis data, the evolution characteristics of air quality and the impact of meteorological conditions on the air quality were analyzed during the G20 summit (from 10 August to 20 September, 2016) in Hangzhou. The results show that due to significant reduction in motor vehicle emissions, the concentration of NO₂ in Hangzhou was lower than that before the implementation of mitigation measures, and the decreasing degree was the highest among all cities. The concentrations of PM_2.5, PM₁₀, SO₂, CO and O₃ increased slightly due to the adverse atmosphere condition, while Hangzhou showed the lowest increase among all surrounding cities during the G20 summit, indicating that the control measures made a great contribution to the improvement of air quality of Hangzhou. The pollutant concentration increased rapidly along with the termination of mitigation measures. The meteorological conditions had an important impact on air quality in Hangzhou-hot weather was favorable for the formation of O₃ and the clean easterly wind brought less pollutants before the implementation of mitigation measures. Thanks to the effective implementation of emergency measures to reduce emissions, the concentration of NO₂ in Hangzhou decreased the most significantly and the concentrations of other pollutants increased slightly lower than that in the surrounding cities in the condition of less precipitation, the stable weather together with outside pollution transport. The meteorological conditions were not conducive to the vertical diffusion of pollutants after G20 summit, and the maximum value of pollutant concentration appeared because of the stable weather and the back-to-normal impact of the pollution sources. The minimum value of PM_2.5, PM₁₀ and O₃ concentrations appeared due to the impact of typhoon "Moranti".